Neuroradiologic diagnosis of minor leak prior to major SAH: Diagnosis by T1-FLAIR mismatch

BACKGROUND AND PURPOSE: In major SAH, the only method to diagnose a preceding minor leak is to ascertain the presence of a warning headache by interview; however, poor clinical condition and recall bias can cause inaccuracy. We devised a neuroradiologic method to diagnose previous minor leak in patients with SAH and attempted to determine whether warning (sentinel) headaches were associated with minor leaks before major SAH. MATERIALS AND METHODS: We retrospectively evaluated 127 patients who were admitted with SAH within 48 hours of ictus. Previous minor leak before major SAH was defined as T1WI-detected clearly bright hyperintense subarachnoid blood accompanied by SAH blood on FLAIR images that was distributed over a larger area than bright hyperintense subarachnoid blood on T1WI (T1-FLAIR mismatch). RESULTS: The incidence of warning headache before SAH was 11.0% (14 of 127 patients, determined by interview). The incidence of T1-FLAIR mismatch (neuroradiologic diagnosis of minor leak before major SAH) was 33.9% (43 of 127 patients). Of the 14 patients with warning headache, 13 had a minor leak diagnosed by T1-FLAIR mismatch at the time of admission. Variables identified by multivariate analysis as significantly associated with minor leak diagnosed by T1-FLAIR mismatch included 80 years of age or older, rebleeding after admission, intracerebral hemorrhage on CT, and mRS scores of 3- 6. CONCLUSIONS: We conclude that warning headaches diagnosed by interview are not a product of recall bias but are the result of actual leaks from aneurysms.